Knife sharpener



FIG. 1 is a top perspective view of the knife sharpener showing my new design.

FIG. 2 is a top view thereof.

FIG. 3 is a bottom view thereof.

FIG. 4 is side view thereof.

FIG. 5 is another side view thereof.

FIG. 6 is front view thereof.

FIG. 7 is a back view thereof; and,

FIG. 8 is another top perspective view thereof.

The broken lines showing other parts of the knife sharpener form no part of the claimed design. 

CLAIM The ornamental design for a knife sharpener, as shown and described. 